Heretofore, thermosetting resins having imide structure have been widely used in industry due to their excellent properties such as electrical insulation, high-temperature stability and dimensional stability of molded articles.
Particularly, the thermosetting resin derived from aromatic bismaleimide is an insoluble and infusible material having excellent high-temperature stability. However, it has drawbacks of inferior impact resistance and poor flexibility.
Therefore, as a method for improving the impact strength and flexibility of the resin derived from aromatic bismaleimide, aromatic bismaleimide was tried to use in combination with aromatic diamines. For example, polyamino-bismaleimide resin (trade mark KERIMIDE, a product from Rhone-Poulenc Ind.) has impact strength and flexibility superior to the resin from aromatic bismaleimide alone. Thus the former resin is widely used for impregnation varnish, laminated boards, molded articles etc.
The above thermosetting resins, however, have been still unsatisfactory in the impact strength and flexibility viewpoint.
Therefore, monomers have not yet been provided for the thermosetting resins being satisfied with these properties.